Primer compositions

ABSTRACT

The present disclosure is drawn to primer compositions, which can include a binder including polyvinyl alcohol, starch nanoparticles, and a crosslinkable polyurethane dispersion. The primer competitions can also include a cationic salt and water.

The present application is a continuation of U.S. patent applicationSer. No. 15/569,346, filed on Oct. 25, 2017, which is a national stageapplication of International Application No. PCT/US2015/047481, each ofwhich incorporated herein by reference.

BACKGROUND

There are several reasons that inkjet printing has become a popular wayof recording images on various media surfaces, particularly paper. Someof these reasons include low printer noise, variable content recording,capability of high speed recording, and multi-color recording.Additionally, these advantages can be obtained at a relatively low priceto consumers. Though there has been great improvement in inkjetprinting, accompanying this improvement are increased demands byconsumers in this area, e.g., higher speeds, higher resolution, fullcolor image formation, increased stability, etc. Additionally, inkjetprinting is becoming more prevalent in high speed commercial printingmarkets, competing with more laborious offset and gravure printingtechnologies. Coated media typically used for these more conventionaltypes of printing, e.g., offset or gravure printing, can performsomewhat acceptably on high speed inkjet printing devices, but thesetypes of media are not always acceptable for inkjet technology as itrelates to image quality, gloss, abrasion resistance, and other similarproperties.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the disclosure will be apparentfrom the detailed description which follows, taken in conjunction withthe accompanying drawings, which together illustrate, by way of example,features of the present technology.

FIG. 1 illustrates a method of coating a media substrate in accordancewith an example of the present technology;

FIG. 2 shows a cross-sectional view of a coated media substrate inaccordance with an example of the present technology; and

FIG. 3 shows a cross-sectional view of a coated media substrate inaccordance with an example of the present technology.

Reference will now be made to several examples that are illustratedherein, and specific language will be used herein to describe the same.It will nevertheless be understood that no limitation of the scope ofthe disclosure is thereby intended.

DETAILED DESCRIPTION

The present disclosure is drawn to primer compositions. In someexamples, the primer compositions can be ink-receiving primercompositions, in that the primer compositions can be used to formcoatings for receiving inks such as inkjet inks. The primer compositionscan be applied to a substrate to form an ink-receiving layer on thesubstrate before printing inkjet ink over or onto the primer layer. Inone example, a primer composition can be applied to offset coated paper.Typically, offset coated papers are significantly different from paperspecifically designed for inkjet printing. Commercial offset paper oftenincludes a smooth, non-porous surface coating that is difficult topenetrate by aqueous liquids. In many cases, offset coatings includeinorganic pigments such as calcium carbonate and clay, as well ashydrophobic polymers that interact poorly with water-based inks.Polymers used in offset media can also sometimes include latex binders,polystyrenes, polyolefins (polypropylene, polyethylene, polybutadiene),polyesters (PET), polyacrylates, polymethacrylates, poly (maleicanhydride), and/or others. As a result of the hydrophobic and non-porousproperties of offset media, water-based inks printed on offset mediaoften have poor image quality, dry very slowly (sometimes taking morethan 24 hours), and have poor durability after drying.

The primer compositions described herein can be applied to a mediasubstrate to improve the ability of the substrate to receive water-basedinks. For example, a primer composition can be coated on a mediasubstrate to improve the durability of images printed with water-basedinks. In one example, a media substrate that is normally less suitablefor printing with water-based inks, such as offset media, can be coatedwith the primer composition prior to printing. This coated mediasubstrate can interact with water-based inks and provided a printedimage with good durability after the ink dries on the coated mediasubstrate.

In further detail, the primer composition can include a water solublepolymeric binder, e.g., at least partially water soluble (at least 5%),mostly water soluble (at least 50%), or fully water soluble (at least99%) in the primer composition. Water soluble polymers can interactbetter with water-based inks compared to the hydrophobic coatings ofoffset media. However, many types of water soluble polymeric binderexhibit poor dry smearfastness immediately after printing due to poorwet film strength. For example, starches, cellulose, polyethylene oxide,and polyvinylpyrrolidone (PVP) are examples of water soluble polymersthat can have poor dry smearfastness when used in primers on offsetmedia.

Poor dry smearfastness immediately after printing can be problematicbecause the printed image can be easily smeared if the image is rubbedor otherwise disturbed soon after printing. For example, when using anHP high speed Web Press®, the printing is a continuous process and thepaper is rewound as a roll after printing. The image or text printed onthe paper can be smeared when the paper is rewound if the dry durabilityis poor. Prior solutions to this problem have included reducing theprinting speed, increasing drying temperature, or increasing the dryingzone. Several disadvantages are associated with these solutions,however. For example, increasing the drying time requires reducing theproduction rate, which increases the cost or time cost of printing.Harsh drying conditions can cause increased paper cockle. Increasing thesize of the drying zone makes the printing system occupy a larger space,which increases the total cost or space cost of printing.

Surprisingly, certain primer compositions including polyvinyl alcoholshave been found to provide much better dry smearfastness immediatelyafter printing. Thus, the primer composition can include polyvinylalcohol as the water soluble polymeric binder. In addition to thepolyvinyl alcohol, the primer composition can include a cationic salt.Thus, the hydroxyl groups of the polyvinyl alcohol can interact with thecationic salt to form a complex-like structure. This structure canresult in enhanced wet film strength of the primer layer and the inkprinted on top of the primer layer. When inkjet ink is printed on top ofthe primer, the ink can have improved instant dry smearfastness.

Although primer compositions including polyvinyl alcohols can providedesirable dry smearfastness, it is difficult to achieve both drysmearfastness and wet smearfastness at the same time. Poor wetsmearfastness can cause poor mechability because the printed substratecan often be rewound before the primer layer and image are completelydry. Mixtures of different water soluble polymeric binders can be usedto adjust the dry smearfastness and wet smearfastness of the primercomposition. However, many mixtures of water soluble polymeric bindersare unable to provide both good dry smearfastness and good wetsmearfastness. For example, mixtures of polyvinyl alcohol with onlylarger particle-sized starch, e.g., 10 μm to 100 μm, can in some casesprovide good dry smearfastness or good wet smearfastness, but not bothat the same time. However, certain primer compositions including amixture of polyvinyl alcohol, starch nanoparticles, and a polyurethanedispersion have been found to provide better dry smearfastness and wetsmearfastness at the same time. This combination of binders has alsobeen found to provide good paper gloss.

The primer composition can be used on offset paper in a continuousprinting system such as the HP high speed Web Press® mentioned above. Insome cases, the instant dry and wet smearfastness of the printed imagecan be such that no smearing occurs when the printed paper is rewoundinto a roll after printing. Because the printed image does not requireextra time to dry before rewinding the paper, the press can run at ahigh speed. These advantages can be obtained without compromising printquality.

With this description in mind, in some examples, the present technologyprovides primer compositions. In one example, a primer composition caninclude from 5 wt % to 70 wt % of a binder which includes a polyvinylalcohol, starch nanoparticles, and a polyurethane dispersion. The primercomposition can also include a cationic salt and water. Additionalingredients that can be included in the primer composition include latexparticles, a wax, and/or a surfactant, in some examples.

The polyvinyl alcohol, starch nanoparticles, and polyurethane dispersioncan act as a binder in the primer composition. Generally, the amount ofthese ingredients can be sufficient to act as a binder to bind theremaining ingredients of the primer composition to the substrate. Insome examples, the binder content of the primer composition can bewithin a range such that there is sufficient binder to bind the otheringredients of the primer to the substrate, but not so much that theink-receiving properties of the primer are compromised. As an example,too much binder can, in some cases, make the primer layer less porousand negatively impact the solution stability of the primer. This caninterfere with the interaction between the primer layer and water-basedinks. In some examples, the total amount of binder present in the primercomposition can be from 5 wt % to 70 wt %. In other examples, the totalamount of binder can be from 5 wt % to 50 wt %, 10 wt % to 30 wt %, or10 wt % to 20 wt %.

In further detail, the primer composition can include polyvinyl alcoholin an amount from 1 wt % to 40 wt %, 2 wt % to 30 wt %, or 5 wt % to 20wt %, based on the weight of all dry components of the primercomposition.

The type of polyvinyl alcohol is not particularly limited with respectto the molecular weight and degree of hydrolysis of the polyvinylalcohol. However, in some examples, the polyvinyl alcohol can have aweight-average molecular weight from 1,000 M_(w) to 300,000 M_(w). Infurther examples, the polyvinyl alcohol can have an average molecularweight from about 20,000 M_(w) to about 250,000 M_(w). In more specificexamples, the polyvinyl alcohol can have an average molecular weightfrom about 27,000 M_(w) to about 205,000 M_(w). The degree of hydrolysisof the polyvinyl alcohol can be from about 75 mol % to about 100 mol %.In certain examples, the degree of hydrolysis can be from about 86 mol %to about 100 mol %. It is believed that the hydroxyl groups on thepolyvinyl alcohol can interact with the cationic salt in the primercomposition to form a complex-like structure, which improves the instantsmearfastness of printed images on a primer coated substrate.Non-limiting examples of polyvinyl alcohols that can be used in theprimer composition include Poval® 4-98 (Kuraray America, Inc.) (27,000M_(w), 98-98.8 mol % hydrolysis); Poval® 13-88 (Kuraray America, Inc.)(86.7-88.7 mol % hydrolysis); Poval® 18-88 (Kuraray America, Inc.)(130,000 M_(w), 86.7-88.7 mol % hydrolysis); Poval® 26-88 (KurarayAmerica, Inc.) (86.7-88.7 mol % hydrolysis); and/or Poval® 40-88(Kuraray America, Inc.) (205,000 M_(w)).

The polyvinyl alcohol can in some cases be a mixture of two or moretypes of polyvinyl alcohol. In such examples, the total amount of thepolyvinyl alcohols can be from 1 wt % to 40 wt %, 2 wt % to 30 wt %, 5wt % to 20 wt %, based on the weight of all dry components of the primercomposition. Whatever range is considered, it is understood that therange relates to total concentrations of polyvinyl alcohol, whetherthere be one, two, three, etc., specific polyvinyl alcohol speciespresent. In one example, the primer composition can include a mixture oftwo types of polyvinyl alcohol having different molecular weights.

In addition to the polyvinyl alcohol, the binder can include starchnanoparticles. Starch is a carbohydrate consisting of linear or branchedpolysaccharide chains. Starch is often available in granular form, withgranules having an average diameter of 10 μm to 100 μm or larger. Starchnanoparticles are different from this common form of starch in that thestarch nanoparticles have a smaller, nano-sized average diameter. Forexample, starch nanoparticles can have an average diameter from 1 nm to1 μm. The starch nanoparticles used in the binder for the present primercompositions can have an average diameter within this range of 1 nm to 1μm. In some examples, the starch nanoparticles can have an averagediameter from 10 nm to 500 nm, 20 nm to 200 nm, or 50 nm to 150 nm.

Non-limiting examples of suitable starch nanoparticles for use in thepresent primer compositions include Ecosphere® 2202D, 2260, 2330 and2326 (EcoSynthetix Inc.). These starch nanoparticles are cross-linkedstarch with a nanoparticle structure, and can yield better durabilitythan traditional starches that are non-crosslinked polymers. In someexamples, the primer composition can include starch nanoparticles in anamount from 1 wt % to 20 wt %, 1 wt % to 10 wt %, or 2 wt % to 5 wt %based on the weight of all dry components of the primer composition.

The binder of the primer composition can also include a polyurethanedispersion. The polyurethane dispersion can be water-based, with littleor no volatile organic content (VOC). Polyurethane dispersions caninclude polyurethane polymer that has already reacted, i.e., the polymeris already formed from monomers such as polyols and isocyanates. Assuch, the polyurethane dispersion can include little or no freeisocyanate.

In some examples, the polyurethane dispersion can be crosslinkable. Insome aspects, the crosslinkable polyurethane dispersion can includecrosslinkable components, such as crosslinkable groups pendant from thepolyurethane polymer. Non-limiting examples of such crosslinkable groupscan include carboxyl, hydroxyl, amino, and mercapto groups. In aspecific example, the crosslinkable polyurethane can include carboxylgroups pendant from the polymer chains of the polyurethane, as terminalgroups on the polymer chains of the polyurethane, or both. In additionalaspects, the crosslinkable polyurethane dispersion can beself-crosslinkable, crosslinkable through addition of a crosslinkingagent, or both. In some examples, the crosslinkable polyurethane can becrosslinked after the primer composition is coated on a substrate byapplication of heat, evaporation of solvent, exposure to actinicradiation such as UV light, or by addition of a crosslinking agent. In aspecific example, the crosslinkable polyurethane can be crosslinkablewithout a crosslinking agent, and the primer composition can besubstantially devoid of crosslinking agent. By “substantially devoid” or“subtantially free of,” what is meant is that the component described iseither completely absent, or is present in only de minimis or residualamounts that do not have an material impact on the nature of thecomposition compared to a composition without any of the componentpresent. In another specific example, the primer composition can includea crosslinking agent to enable or increase the rate of crosslinking. Incertain examples, the crosslinkable polyurethane dispersion can beconfigured to crosslink after the primer composition is coated on asubstrate, before the substrate is rewound at the rewinding station of ahigh speed press. The polyurethane can crosslink before ink is printedover the primer layer, while ink is printed over the primer layer, afterink is printed over the primer layer, or combinations thereof. In somecases, the polyurethane can at least partially crosslink before thesubstrate is rewound at the rewinding station, although additionalcrosslinking can occur after rewinding. Without being bound to aspecific mechanism, it is believed that crosslinking of the polyurethanedispersion after coating the substrate with the primer composition cancontribute to the durability of the primer layer and images printedthereon.

Adding the polyurethane dispersion to the polyvinyl alcohol and starchnanoparticles can produce a binder that provides good dry and wetsmearfastness. This binder can also provide good gloss to the substratecoated with the primer composition. In some examples, the polyurethanedispersion can be present in the primer composition in an amount from 1wt % to 20 wt %, 1 wt % to 10 wt %, or 2 wt % to 5 wt % based on theweight of all dry components of the primer composition. In certainexamples, the polyurethane dispersion can be present in an equal amountas the starch nanoparticles. Non-limiting examples of suitablepolyurethane dispersions for use in the present primer compositions caninclude Sancure® 20041, 20037F, 20025F, 13094HS, 2715 and 861 (LubrizolAdvanced Materials, Inc.), Acrysol™ RM-2020 (Dow Chemical Company),PrintRite™ DP376 (Lubrizol Advanced Materials, Inc.), and Lucidene™ 645(Dow Chemical Company).

In some cases, the primer composition can include additional binders.Non-limiting examples of such binders include cellulose, polyethyleneoxide, polyvinyl pyrrolidone, and others. The additional binders canalso be mixtures of two or more water soluble polymeric binders. In someexamples, if additional binders are present then the additional binderscan be present in a smaller amount than the combined polyvinyl alcohol,starch nanoparticles, and polyurethane dispersion. In further examples,the combined polyvinyl alcohol, starch nanoparticles, and polyurethanedispersion can make up at least 10 wt % by dry weight of all binderspresent in the primer composition. In still further examples, thecombined polyvinyl alcohol, starch nanoparticles, and polyurethanedispersion can make up at least 80 wt % by dry weight of all binderspresent in the primer composition. In a specific example, the primercomposition can be substantially free of any binder other than thepolyvinyl alcohol, starch nanoparticles, and polyurethane dispersion.

The primer composition can also include a cationic salt. The cationicsalt can be present in an amount sufficient to immobilize pigmentcolorants in the ink to be printed over the primer and to yield goodimage quality. In some examples, the primer composition can include thecationic salt in an amount from 10 wt % to 50 wt %, 10 wt % to 40 wt %,15 wt % to 30 wt %, or 20 wt % to 30 wt % based on the weight of all drycomponents of the primer composition.

The cationic salt can include a metal cation. In some examples, themetal cation can be sodium, calcium, copper, nickel, magnesium, zinc,barium, iron, aluminum, chromium, or other metal. The cationic salt canalso include an anion. In some examples, the anion can be fluoride,chloride, iodide, bromide, nitrate, chlorate, acetate, or RCOO⁻ where Ris hydrogen or any low molecular weight hydrocarbon chain, e.g., C1 toC12. In a more specific example, the anion can be a carboxylate derivedfrom a saturated aliphatic monocarboxylic acid having 1 to 6 carbonatoms or a carbocyclic monocarboxylic acid having 7 to 11 carbon atoms.Examples of saturated aliphatic monocarboxylic acid having 1 to 6 carbonatoms may include formic acid, acetic acid, propionic acid, butyricacid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid,and/or hexanoic acid. In some cases, the cationic salt can be apolyvalent metal salt made up of a divalent or higher polyvalentmetallic ion and an anion. In certain examples, the cationic salt caninclude calcium chloride, calcium nitrate, magnesium nitrate, magnesiumacetate, and/or zinc acetate. In one aspect, the cationic salt caninclude calcium chloride or calcium nitrate (CaCl₂ or Ca(NO₃)₂). In oneadditional specific aspect, the cationic salt can include calciumchloride (CaCl₂). The cationic salt can also be a mixture of two or moredifferent cationic salts. In such examples, the total amount of themixture of cationic salts can be 10 wt % to 50 wt %, 10 wt % to 40 wt %,15 wt % to 30 wt %, or 20 wt % to 30 wt % based on the weight of all drycomponents of the primer composition. Whatever range is considered, itis understood that the range relates to total concentrations of salts,whether there be one, two, three, etc., specific salt species present.

The primer composition can also include latex particles. In someexamples, the latex particles can be present in an amount from about 10wt % to about 70 wt % based on the weight of all dry components of theprimer composition. In further examples, the latex particles can bepresent in an amount from 20 wt % to 60 wt % based on the weight of alldry components of the primer composition. Additionally, the primercomposition can be predominantly (greater than 50 wt % by dry weight)made up of the latex particles, the polyvinyl alcohol, the starchnanoparticles, the polyurethane dispersion, and the cationic salt. Inone example, the polyvinyl alcohol, starch nanoparticles, polyurethanedispersion, cationic salt, and latex particles can make up at least 80wt % of all dry ingredients in the primer composition.

The latex particles can be used to improve the film strength of theprimer layer. In one example, the glass transition temperature (Tg) ofthe latex can be from 0° C. to 100° C. The latex polymer can be anionic,nonionic, or cationic. In some examples, the latex particles can becationic latex particles.

In other examples, the latex particles can be made of polymers andcopolymers including acrylic polymers or copolymers, vinyl acetatepolymers or copolymers, polyester polymers or copolymers, vinylidenechloride polymers or copolymers, butadiene polymers or copolymers,styrene-butadiene polymers or copolymers, acrylonitrile-butadienepolymers or copolymers. In another example, the latex particles caninclude a vinyl acetate-based polymer, an acrylic polymer, a styrenepolymer, a styrene-butadiene (SBR)-based polymer, a polyester-basedpolymer, a vinyl chloride-based polymer, an acid-based polymer, or thelike. In one aspect, the latex particles can be a polymer or a copolymerincluding acrylic polymers, vinyl-acrylic copolymers andacrylic-polyurethane copolymers. In another aspect, the latex particlescan be cationic acrylate latex. In one specific aspect, the latex can bea vinyl acetate polymer. In another specific aspect, the latex can be aSBR polymer.

Generally, the latex particles can have a weight average molecularweight (M_(w)) of 5,000 M_(w) to 500,000 M_(w). In one example, thelatex particles can range from 150,000 M_(w) to 300,000 M_(w). In someexamples, the average particle diameter of the latex particles can befrom 10 nm to 1 μm and, as other examples, from 10 nm to 500 nm, and inyet other examples, from 50 nm to 250 nm. The particle size distributionof the latex is not particularly limited, and either latex having abroad particle size distribution or latex having a mono-dispersedparticle size distribution may be used. It is also possible to use twoor more kinds of polymer fine particles each having a mono-dispersedparticle size distribution in combination.

Many coating compositions for inkjet printing include inorganic pigmentsto improve the absorption properties of the coating. Such inorganicpigments can include, for example, clays such as kaolin clay or calcinedclay, ground calcium carbonate, precipitated calcium carbonate, bariumsulfate, titanium dioxide, silica, aluminum trihydrate, aluminum oxide,boehmite, or combinations thereof. However, in some examples, thepresent primer composition can be substantially devoid of inorganicpigments. In other examples, the primer composition can include aninorganic pigment. In some examples, the primer composition can includean inorganic pigment in an amount of about 5 wt % or less of all drycomponents of the primer composition. Thus, the primer composition caninclude a relatively small amount of inorganic pigment, such as lessthan 5 wt %. In certain examples, the primer composition can be acidicand can include an inorganic pigment that is compatible with acid, suchas a clay.

In further examples, the primer composition can include other additivessuch as slip aids that contribute to abrasion resistance and coefficientof friction (COF) reduction. For example, a wax can be included as aslip aid. Suitable waxes can include particles of a synthetic wax,natural wax, combinations of a synthetic wax and a natural wax,combinations of two or more different synthetic waxes, or combinationsof two or more different natural waxes, for example. In some examples,the synthetic wax can include polyethylene, polypropylene,polybutadiene, polytetrafluoroethylene, polyvinylfluoride,polyvinyldiene fluoride, polychlorotrifluoroethylene, perfluoroalkoxypolymer, perfluoropolyether, polyurethane,polyethylenechlorotrifluoroethylene, polyethylene-vinyl acetate, epoxyresin, silicone resin, polyamide resin, polyamide, or polyester resin.In some examples, the natural wax can include carnauba wax, paraffinwax, montan wax, candelilla wax, ouricury wax, sufarcane wax, retamowax, or beeswax. In one example, the wax can be a polyethylene wax, suchas a high density polyethylene wax. Commercially available slip aidsthat can be used include Michemshield® 29235 (Michelman, Inc.),Ultralube® E846 (Keim-Additec Surface GmbH), and Ultralube® D-806(Keim-Additec Surface GmbH), for example. In some examples, a wax can bepresent in the primer composition at an amount of 1 wt % to 20 wt % ofall dry ingredients in the primer composition. In other examples, thewax can be present in an amount of 5 wt % to 15 wt % of all dryingredients in the primer composition.

The primer composition can also include other coating additives such assurfactants, rheology modifiers, defoamers, optical brighteners,biocides, pH controlling agents, dyes, and other additives for furtherenhancing the properties of the primer composition. The total amount ofsuch optional coating additives can be present, individually, in therange of 0.01 wt % to 5 wt % of all dry ingredients of the primercomposition.

The present technology also extends to methods of coating a mediasubstrate. FIG. 1 provides an exemplary method of coating a mediasubstrate 100. The method includes applying 110 a primer composition toa media substrate, wherein the primer composition includes a binderincluding polyvinyl alcohol, starch nanoparticles, and a polyurethanedispersion. The primer composition further includes a cationic salt, andwater.

The primer composition used in the method can have any of theingredients in the amounts described above with respect to the primercomposition. In a particular example, the method can include applying aprimer composition that includes the polyvinyl alcohol in an amount from1 wt % to 40 wt % of all dry ingredients in the primer composition,starch nanoparticles in an amount from 1 wt % to 20 wt %, and apolyurethane dispersion in an amount from 1 wt % to 20 wt % of all dryingredients in the primer composition. In another example, the methodcan include applying a primer composition that includes latex particlespresent in an amount from 20 wt % to 70 wt % of all dry components ofthe primer compositions. In a further example, the method can includeapplying a primer composition in which polyvinyl alcohol, starchnanoparticles, polyurethane dispersion, latex particles, and cationicsalt make up at least 80 wt % of all dry ingredients in the primercomposition. In yet another example, the method can include applying aprimer composition that is substantially devoid of inorganic pigments.

The composition can be applied to the substrate by any of a number ofcoating methods. In accordance with examples of the present disclosure,the substrate can be coated by spray coating, dip coating, cascadecoating, roll coating, gravure coating, curtain coating, air knifecoating, cast coating, Meyer rod coating, blade coating, film coating,metered size press coating, puddle size press coating, calender stack,and/or by using other known coating techniques. The thickness selectedfor the coating layer can vary. In one example, the primer compositioncan be applied at a dry coat weight from 0.1 gsm to 20 gsm. In anotherexample, the primer composition can be applied to the substrate at a drycoat weight from 0.3 gsm to 10 gsm. In another example, the primercomposition can be applied to the substrate at a dry coat weight from0.3 gsm to 5 gsm. In another example, the primer composition can beapplied to the substrate at a dry coat weight from 0.3 gsm to 1 gsm.

The method of coating the media substrate can further include allowing asufficient time for the primer layer to dry before printing ink on theprimer layer. The primer layer can be dried with infrared lamp, hot airand combination thereof. The primer layer can retain from about 0.01 wt% to about 10 wt % water, based on the total weight of the coating, whenthe coating is dry enough to print on. In some examples, the coating canhave from about 1 wt % to about 6 wt % water remaining when an image isprinted on the coated substrate. Thus, it is understood that the “drycoat weight” described herein refers to dry components, even if somewater remains behind in the final formulation coating.

Ink can be printed on the primer layer. Printing can occur when theprimer layer is partially dry or fully dry (i.e. dry to the touch butstill may include some residual water). In some cases, the ink can be awater-based ink such as a water-based inkjet ink. Inkjet inks generallyinclude a colorant dispersed or dissolved in an ink vehicle. As usedherein, “liquid vehicle” or “ink vehicle” refers to the liquid fluid inwhich a colorant is placed to form an ink. Ink vehicles are well knownin the art, and a wide variety of ink vehicles may be used with thesystems and methods of the present disclosure. Such ink vehicles mayinclude a mixture of a variety of different agents, including,surfactants, solvents, co-solvents, anti-kogation agents, buffers,biocides, sequestering agents, viscosity modifiers, surface-activeagents, water, etc. Though not part of the liquid vehicle per se, inaddition to the colorants, the liquid vehicle can carry solid additivessuch as polymers, latexes, UV curable materials, plasticizers, etc.

Generally the colorant discussed herein can include a pigment and/ordye. As used herein, “dye” refers to compounds or molecules that impartcolor to an ink vehicle. As such, dye includes molecules and compoundsthat absorb electromagnetic radiation or certain wavelengths thereof.For example, dyes include those that fluoresce and those that absorbcertain wavelengths of visible light. In most instances, dyes are watersoluble. Furthermore, as used herein, “pigment” generally includespigment colorants, magnetic particles, aluminas, silicas, and/or otherceramics, organo-metallics or other opaque particles. In one example,the colorant can be a pigment.

Typical ink vehicle formulations can include water, and can furtherinclude co-solvents present in total at from 0.1 wt % to 40 wt %,depending on the jetting architecture, though amounts outside of thisrange can also be used. Further, additional non-ionic, cationic, and/oranionic surfactants can be present, ranging from 0.01 wt % to 10 wt %.In addition to the colorant, the balance or much of the remaining offormulation components can be purified water. Other solids can likewisebe present in the inkjet ink, such as latex particles.

Consistent with the formulation of this disclosure, various otheradditives may be employed to enhance the properties of the inkcomposition for specific applications. Examples of these additives arethose added to inhibit the growth of harmful microorganisms. Theseadditives may be biocides, fungicides, and other microbial agents, whichare routinely used in ink formulations. Examples of suitable microbialagents include, but are not limited to, NUOSEPT® (Nudex, Inc.),UCARCIDE™ (Union carbide Corp.), VANCIDE® (R.T. Vanderbilt Co.), PROXEL®(ICI America), ACTICIDE® (Thor Specialties Inc.) and combinationsthereof.

The present technology also extends to coated media substrates. Themedia substrate can include a variety of types of base substrate,including paper media, nonporous media, swellable media, microporousmedia, photobase media, offset media, coated media, uncoated media, andother types of media including plastics, vinyl media, fabrics, wovensubstrate, etc. In certain examples, the substrate can be a swellablemedia, a microporous media, or an offset media. The primer compositionaccording to the present technology can be especially useful for coatingoffset media, which typically has a small pore diameter and hydrophobicsurface that does not interact well with water based inks.

In one example, a coated media substrate according to the presenttechnology can include a media substrate and a primer layer coated on asurface of the media substrate. The primer layer can include a binderhaving polyvinyl alcohol, starch nanoparticles, and a polyurethanedispersion. The primer layer can also include a cationic salt.

FIG. 2 shows an example of a coated media substrate 200. A basesubstrate 210 is coated with a primer layer 220. On top of the primerlayer, ink jet ink 230 can be printed to form a printed image. The imagecan have improved instant dry smearfastness after printing.

FIG. 3 shows another example of a coated media substrate 300. In thisexample, the base substrate 310 has a primer layer 320 coated on bothsides of the base substrate. Ink jet ink 330 is used to print images oneor on both sides of the coated substrate. Thus, the coated mediasubstrate can be used for double sided printing. Although not shown inthe figures, the base substrate can also include its own coating, suchas the hydrophobic coating on offset paper. Certain coatings (orpre-coatings) described herein can often already be present as part of asubstrate, and these coatings are not the same as the primer layerprimarily discussed in the context of the present disclosure. Offsetmedia or photobase, for example, already include coatings on one or bothside of a substrate material (and thus are considered to be part of thebase substrate). The primer compositions of the present disclosure,conversely, are those which are overcoated with respect to thepre-applied coatings, or alternatively, to substrates that are notalready pre-coated. Such coatings, i.e. the pre-coating and/or theprimer compositions of the present disclosure, can be present on eitherone side of a media substrate or both.

The primer layer on the coated substrate can be formed by applying theprimer compositions disclosed herein using any of the methods disclosedherein. As such, the primer layer can include any of the additionalingredients in any of the amounts disclosed for the primer compositionsdescribed herein. In a specific example, the polyurethane dispersion inthe primer layer of the coated media substrate can be a crosslinkablepolyurethane dispersion. In another specific example, the primer layercan include latex particles in an amount from 10 wt % to 70 wt % of alldry components of the primer layer. Additionally, the polyvinyl alcohol,starch nanoparticles, polyurethane dispersion, latex particles, andcationic salt make up at least 80 wt % of all dry components of theprimer layer.

In yet another example of the present technology, a printing system caninclude an inkjet ink and a coated media substrate as described above.The coated media substrate can include a media substrate and a primerlayer coated on a surface of the media substrate. The primer layer caninclude a polyvinyl alcohol, starch nanoparticles, a polyurethanedispersion, and a cationic salt.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessthe content clearly dictates otherwise.

“Substrate” or “media substrate” includes any base material that can becoated in accordance with examples of the present disclosure, such asfilm base substrates, polymer substrates, conventional paper substrates,photobase substrates, offset media substrates, and the like. Further,pre-coated and film coated substrates can be considered a “substrate”that can be further coated in accordance with examples of the presentdisclosure.

“Slip aid” refers to materials that can be added to coating compositionsherein to provide abrasion resistance to coatings of the presentdisclosure.

“Instant dry smearfastness” refers to the ability of a printed image toresist smearing when rubbed with a dry instrument such as a finger or aRubber Eraser Tool, immediately after printing or within a short time ofbeing printed. The short time can be, for example, from 1 second to 30seconds, from 1 second to 20 seconds, or from 5 seconds to 10 seconds.In some cases, the short time can be the time required for a printedimage to travel from the inkjet printer to a rewinding roll. In oneexample, a printed image on an HP T200 Web Press® takes from 5 secondsto 10 seconds to reach the rewinder after being printed.

“Instant wet smearfastness” refers to the ability of a printed image toresist smearing when rubbed with a wet instrument such as a wet fingerimmediately after printing or within a short time of being printed. Theshort time can be, for example, from 1 second to 30 seconds, from 1second to 20 seconds, or from 5 seconds to 10 seconds. In some cases,the short time can be the time required for a printed image to travelfrom the inkjet printer to a rewinding roll. In one example, a printedimage on an HP T200 Web Press® takes from 5 seconds to 10 seconds toreach the rewinder after being printed.

“Instant mechability” refers to the instant dry and wet smearfastnessand the scratch resistance of a sample after printing, drying, andreaching the rewinding station.

When referring to “high speed” as it related to a digital printingpress, presses such as the HP T200 Web Press® or the HP T300 Web Press®exhibit printing speeds that are commensurate of what is considered tobe “high speed.” For example, the HP T300 Web Press® can print textand/or other images on media at a rate of 400 feet per minute. Thiscapability would be considered high speed. In another example, and moregenerally, printing at 100 feet per minute would also be considered highspeed.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be “alittle above” or “a little below” the endpoint. The degree offlexibility of this term can be dictated by the particular variable andcan be determined based on experience and the associated descriptionherein.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, dimensions, amounts, and other numerical data may bepresented herein in a range format. It is to be understood that suchrange format is used merely for convenience and brevity and should beinterpreted flexibly to include not only the numerical values explicitlyrecited as the limits of the range, but also to include all theindividual numerical values or sub-ranges encompassed within that rangeas if each numerical value and sub-range is explicitly recited. Forexample, a weight ratio range of about 1 wt % to about 20 wt % should beinterpreted to include not only the explicitly recited limits of 1 wt %and about 20 wt %, but also to include individual weights such as 2 wt%, 11 wt %, 14 wt %, and sub-ranges such as 10 wt % to 20 wt %, 5 wt %to 15 wt %, etc.

As a further note, in the present disclosure, it is noted that whendiscussing the coated media substrate, the method of coating asubstrate, or the primer compositions herein, each of these discussionscan be considered applicable to each of these examples, whether or notthey are explicitly discussed in the context of that example. Thus, forexample, in discussing details about the coated media substrate per se,such discussion also refers to the methods and primer compositionsdescribed herein, and vice versa.

The following examples illustrate some of the primer compositions,coated media substrates, systems, and methods that are presently known.However, it is to be understood that the following are only exemplary orillustrative of the application of the principles of the presentcompositions, systems, and methods. Numerous modifications andalternative compositions, systems, and methods may be devised withoutdeparting from the spirit and scope of the present disclosure. Theappended claims are intended to cover such modifications andarrangements. Thus, while the examples have been described above withparticularity, the following provide further detail in connection withwhat are presently deemed to be the acceptable examples.

EXAMPLES

Formulation Examples 1-10 were prepared according to Tables 1A and 1B.Examples 2-10 are examples prepared according to the present technologyand Example 1 is a comparative example.

TABLE 1A Example No. Ingredient Dry Wt % 1 2 3 4 5 Poval ® 13-88 8 8 8 88 (polyvinyl alcohol) Poval ® 18-88 3 3 3 3 3 (polyvinyl alcohol)Ecosphere ® 2202D 4 4 4 4 4 (starch nanoparticles) Litex ® 9710 52 50 5050 50 (carboxylated butadiene acrylonitrile copolymer latex) Sancure ®20041 4 (cross-linking polyurethane dispersion) Acrysol ™ RM-2020 4(polyurethane dispersion) PrintRite ™ DP376 4 (polyurethane dispersion)Lucidene ™ 645 4 (polyurethane dispersion) Ultralube ® D-806 10 10 10 1010 (polyethylene wax) Calcium Chloride 22 20 20 20 20 (cationic salt)TEGO Wet 510 1 1 1 1 1 (surfactant)

TABLE 1B Example No. Ingredient Dry Wt % 6 7 8 9 10 Poval ® 13-88 8 8 88 8 (polyvinyl alcohol) Poval ® 18-88 3 3 3 3 3 (polyvinyl alcohol)Ecosphere ® 2202D 4 4 4 4 4 (starch nanoparticles) Litex ® 9710 52 50 5050 50 (carboxylated butadiene acrylonitrile copolymer latex) Sancure ®20037F 4 (cross-linking polyurethane dispersion) Sancure ® 20025F 4(cross-linking polyurethane dispersion) Sancure ® 13094HS 4(cross-linking polyurethane dispersion) Sancure ® 2715 4 (cross-linkingpolyurethane dispersion) Sancure ® 861 4 (cross-linking polyurethanedispersion) Ultralube ® D-806 10 10 10 10 10 (polyethylene wax) CalciumChloride 22 20 20 20 20 (cationic salt) TEGO Wet 510 1 1 1 1 1(surfactant) Poval ® (from Kuraray America, Inc.) Ultralube ® (fromKeim-Additec Surface GmbH) TEGO ® (from Evonik Resource Efficiency GmbH)Ecosphere ® (from EcoSynthetix Inc.) Litex ® (from Synthomer LLC)Sancure ® (from Lubrizol Advanced Materials, Inc.) Acrysol ™ (from DowChemical Company) PrintRite ™ (from Lubrizol Advanced Materials, Inc.)Lucidene ™ (from Dow Chemical Company)

The Example formulations 1-10 were coated onto Sterling® Ultra Gloss(Verso Corporation), 60# paper with 2 g/m² (gsm) of dry coating weight.Samples were printed with an HP CM8060 MFP Edgeline printer, fromHewlett-Packard Co., Palo Alto, Calif., USA (HP), using HP A50 pigmentinks (i.e. aqueous inkjet ink for digital inkjet printing). The printingprocess used involved 2 passes and six dry spin conditions to mimichigh-speed, digital, web press inkjet printing. Dry and wetsmearfastness refer to the ability of the printed image to resistappearance degradation upon rubbing or smearing the image by dry or wetfinger. For the dry and wet finger smearfastness tests, a dry or wetfinger was placed against a printed area, pushed with force of about 50g/in², and drawn toward the tester. The finger was then released tocheck the tested area.

The results of the dry finger smearfastness test, wet fingersmearfastness test, and sheet gloss are shown in Tables 2A and 2B. Forthe dry and wet finger smearfastness tests, the visual ranking is basedon a 1 to 5 scale, with 1 being the worst and 5 being the best. Aranking equal to or greater than 3 is considered good and acceptable. Aranking below 3 is considered poor and not acceptable. A BYK GardnerGloss meter is used to measure sheet gloss at 75 degrees. The unit ofgloss is %.

TABLE 2A Visual Ranking of Performance Example No. 1 2 3 4 5 Instant dryfinger smearfastness 3 3 3.5 3 3.5 Instant wet finger smearfastness 2.753 3 3 3 Wet finger smearfastness after 7 days 2.75 3 3 3 3.75 Sheetgloss at 75 degrees 60 51 4.5 54 58

TABLE 2B Visual Ranking of Performance Example No. 6 7 8 9 10 Instantdry finger smearfastness 3.5 3.2 3.5 3.2 3.2 Instant wet fingersmearfastness 3 3 3 3 3 Wet finger smearfastness after 7 days 3.75 3.53.75 3.5 3.5 Sheet gloss at 75 degrees 62 68 61 79 78

Examples 2-10, which included polyvinyl alcohol, starch nanoparticles,and polyurethane dispersions, provided acceptable durability, withExamples 5, 6, and 8 providing the best overall performance. ComparativeExample 1, which did not include a polyurethane dispersion, but includedpolyvinyl alcohol and starch nanoparticles as well as latex particles,provided poor wet finger smearfastness. Examples 2 to 4 showed low glossnumbers indicating that these polyurethane polymers are not compatiblewith the metal salt, resulting in lower gloss. The other types ofpolyurethane polymers such as Sancure 20041, 20037F, 20025F, 13094hs,2715 and 861 showed higher gloss, indicating that they are compatiblewith metal salt.

While the disclosure has been described with reference to certainexamples, various modifications, changes, omissions, and substitutionscan be made without departing from the spirit of the disclosure. It isintended, therefore, that the disclosure be limited only by the scope ofthe following claims.

What is claimed is:
 1. A primer composition, comprising: 5 wt % to 70 wt% of a binder including polyvinyl alcohol, starch nanoparticles, and acrosslinkable polyurethane dispersion; a cationic salt; and water. 2.The primer composition of claim 1, wherein the primer composition issubstantially devoid of crosslinking agent.
 3. The primer composition ofclaim 1, wherein the cationic salt is present in an amount from 10 wt %to 40 wt % of all dry components of the primer composition.
 4. Theprimer composition of claim 1, further comprising latex particlespresent in an amount from 10 wt % to 70 wt % of all dry components ofthe primer composition.
 5. The primer composition of claim 4, whereinthe polyvinyl alcohol, the starch nanoparticles, the crosslinkablepolyurethane dispersion, the latex particles, and the cationic salt makeup at least 80 wt % of all of dry components of the primer composition.6. The primer composition of claim 1, wherein the polyvinyl alcohol is amixture of two different polyvinyl alcohols with differentweight-average molecular weights.
 7. The primer composition of claim 1,wherein the primer composition is substantially devoid of inorganicpigments.
 8. The primer composition of claim 1, wherein the primercomposition further comprises an inorganic pigment in an amount of about5 wt % or less of all dry components of the primer composition.
 9. Theprimer composition of claim 1, wherein the polyvinyl alcohol has adegree of hydrolysis ranging from 75 mol % to 100 mol %, and whereinhydroxyl groups on the polyvinyl alcohol interact with the cationic saltto form a complex.
 10. The primer composition of claim 1, wherein thepolyurethane dispersion is present in an amount from 1 wt % to 20 wt %of all dry components of the primer composition, and wherein the starchnanoparticles are cross-linked.
 11. A method of coating a mediasubstrate, comprising applying a primer composition to a mediasubstrate, wherein the primer composition comprises: from 5 wt % to 70wt % binder including polyvinyl alcohol, starch nanoparticles, and acrosslinkable polyurethane dispersion; a cationic salt; and water. 12.The method of claim 11, wherein the primer composition further compriseslatex particles in an amount from 10 wt % to 70 wt % of all drycomponents of the primer composition, and wherein the polyvinyl alcohol,the starch nanoparticles, the crosslinkable polyurethane dispersion, thelatex particles, and the cationic salt make up at least 80 wt % of alldry components of the primer composition.
 13. A coated media substrate,comprising: a media substrate; and an ink-receiving primer layer coatedon a surface of the media substrate, the primer layer, comprising: from5 wt % to 70 wt % binding including polyvinyl alcohol, starchnanoparticles, and a crosslinkable polyurethane dispersion; and acationic salt.
 14. The coated media substrate of claim 13, wherein thepolyurethane dispersion is a crosslinkable polyurethane dispersion. 15.The coated media substrate of claim 13, wherein the primer layer furthercomprises latex particles in an amount from 10 wt % to 70 wt % of alldry components of the primer layer, and wherein the polyvinyl alcohol,the starch nanoparticles, the crosslinkable polyurethane dispersion, thelatex particles, and the cationic salt make up at least 80 wt % of alldry components of the primer layer.